Xu Hualei, Zhang Liangjun, Wang Jie, Jiang Houshun
Cooperative Innovation Center of Unconventional Oil and Gas, Yangtze University, Wuhan 430100, China.
Hubei Key Laboratory of Drilling and Production Engineering for Oil and Gas, Yangtze University, Wuhan 430100, China.
Polymers (Basel). 2023 Sep 11;15(18):3732. doi: 10.3390/polym15183732.
Temporary plugging diversion fracturing (TPDF) technology has been widely used in various oil fields for repeated reconstruction of high-water-cut old oil wells and horizontal well reservoir reconstruction. Previous studies have carried out in-depth study on the pressure-bearing law and placement morphology of different types of temporary plugging agents (TPAs) in fractures, but there are relatively few studies on TPA accumulation body permeability. To solve this problem, an experimental device for evaluating the TPA performance with adjustable fracture pores is proposed in this paper. Based on the test of fracturing fluid breaking time and residue content, the low damage of fracturing fluid to the reservoir is determined. The TPA degradation performance test determines whether the TPA causes damage to the hydraulic fracture after the temporary plugging fracturing. Finally, by testing the TPA pressure-bearing capacity and the temporary plugging aggregation body permeability, the plugging performance and the aggregation body permeability are determined. The results show the following: (1) Guar gum fracturing fluid shows good gel-breaking performance under the action of breaking agent, and the recommended concentration of breaking agent is 300 ppm. At 90~120 °C, the degradation rate of the three types of TPAs can reach more than 65%, and it can be effectively carried into the wellbore during the fracturing fluid flowback stage to achieve the effect of removing the TPA in the fracture. (2) The results of the pressure-bearing performance of the TPA show that the two kinds of TPAs can quickly achieve the plugging effect after plugging start: the effect of ZD-2 (poly lactic-co-glycolic acid (PLGA)) particle-and-powder combined TPA on forming an effective temporary plugging accumulation body in fractures is better than that of ZD-1 (PLGA) pure powder. There are large pores between the particles, and the fracturing fluid can still flow through the pores, so the ZD-3 (a mixture of lactide and PLGA) granular temporary plugging agent cannot form an effective plugging. (3) The law of length of the temporary plugging accumulation body shows that the ZD-2 combined TPA has stronger plugging ability for medium-aperture simulated fracture pores, while the ZD-1 powder TPA has stronger plugging ability for small aperture simulated fracture pores, and the ZD-3 granular TPA should be avoided alone as far as possible. This study further enriches and improves the understanding of the mechanism of temporary plugging diverting fracturing fluid.
暂堵转向压裂（TPDF）技术已在各油田广泛应用于高含水老油井重复改造及水平井储层改造。以往研究对不同类型暂堵剂（TPA）在裂缝中的承压规律和放置形态进行了深入研究，但对TPA堆积体渗透率的研究相对较少。为解决这一问题，本文提出了一种具有可调裂缝孔隙的TPA性能评价实验装置。基于压裂液破胶时间和残渣含量测试，确定了压裂液对储层的低伤害。TPA降解性能测试确定了暂堵压裂后TPA是否会对水力裂缝造成伤害。最后，通过测试TPA承压能力和暂堵聚集体渗透率，确定封堵性能和聚集体渗透率。结果表明：（1）瓜胶压裂液在破胶剂作用下表现出良好的破胶性能，破胶剂推荐浓度为300 ppm。在90~120℃时，三种TPA的降解率均可达到65%以上，且在压裂液返排阶段能有效携带至井筒，实现裂缝中TPA的清除效果。（2）TPA承压性能结果表明，两种TPA封堵启动后能快速达到封堵效果：ZD-2（聚乳酸-羟基乙酸共聚物（PLGA））颗粒与粉末复合TPA在裂缝中形成有效暂堵堆积体的效果优于ZD-1（PLGA）纯粉末。颗粒间存在较大孔隙，压裂液仍可通过孔隙流动，因此ZD-3（丙交酯与PLGA混合物）颗粒暂堵剂不能形成有效封堵。（3）暂堵堆积体长度规律表明，ZD-2复合TPA对中孔径模拟裂缝孔隙的封堵能力较强，而ZD-1粉末TPA对小孔径模拟裂缝孔隙的封堵能力较强，应尽量避免单独使用ZD-3颗粒TPA。本研究进一步丰富和完善了对暂堵转向压裂液作用机理的认识。
